For problems related to the HTML 5 media elements (<video> and <audio>) -- including WebM, MP4, MSE and EME issues. This would also typically include decoding problems in the codecs themselves (e.g. VP8, VP9, H.264, AAC) experienced during playback.

Comment on attachment 8903797[details]Bug 1394591 - P6. Simplify some internal codec mimetype.
https://reviewboard.mozilla.org/r/175554/#review180700
The codec name is listed in the about:media, so seeing video/webm; codec=vp9 rather than just vp9 is cumbersome. It wasn't even aa pemimety
> Are you sure these tests are not used externally too? (e.g. from HTMLMediaElement::CanPlaytype)
Yes. This is just to determine the codec. The mimetype used with JS and externally and will be aa container one. This mimetype is set from the webm demuxer.